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Wiring Aprilaire humidifier to Honeywell thermostat

Same issue I just had with my heat pump and humidifier install. I temporarily had mine hooked to a relay through the G wire and had a seperate transformer for the humdifier but have recently bought a White-Rodgers thermostat that has a humidity feature built in.

You dont want to hook it to Y, otherwise it will run in the summer also. Same with leaving it attached to G, fine for now but will also run in the summer.

Wiring Aprilaire humidifier to Honeywell thermostat

Did you wire in a humidistat? If you hook the humidifier to G, you will be able to run just the fan only if you need to humidify without a heating call.

Also, did you plum it to hot water? Works better with a heat pump that way.

Yes, I wired it per Aprilaire instructions, so if humidity is called for, it will turn on the fan. Yes, I also ran the hot water to it. Now, I'm off the the hardware store to find some insulation for 1/4" copper tubing. The air handler is located in a cold garage.

Wiring Aprilaire humidifier to Honeywell thermostat

Just to wrap this and to make it official, I just got a reply from Tech Support at Aprilaire:

Dear Mr. MurphyMan,
Thank you for contacting us with regards to your model 400 Humidifier. Without a W terminal, you can eliminate that wire. Y is not needed as G is still called for and accompanies any Y call. We recommend the same wiring for heat pump and heat/cool systems, otherwise.
Please let us know if you have any further questions.
Sincerely,